The present invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to processes for controlling developer aging characteristics. In embodiments, the present invention relates to processes where the developer A.sub.t increases, that is for example where the A.sub.t transient is initially relatively low and increases to a stable value after usage, especially at constant toner concentrations. Moreover, in embodiments the process of the present invention enables a higher toner triboelectric charge and excellent toner yields, which toner yield is inversely dependent upon the developed mass, which is dependent on the toner tribo, and thus a higher toner tribo, for example equal to or greater than 20 microcoulombs per gram. With the processes of the present invention, the values of A.sub.t increased as indicated herein, as determined from the following calculation, that is the product of 3.5 plus the toner concentration (TC) multiplied by the charge Q/M. EQU A.sub.t =(3.5+TC)Q/M
The desired A.sub.t developer tribo, and toner concentrations are, for example, in embodiments from about 120 to about 230 units for A.sub.t, from about 12 to about 23 microcoulombs per gram for tribo (Q/M), and a toner concentration of from about 6 to about 10. The toner and developer compositions of the present invention in embodiments thereof possess excellent admix characteristics as indicated herein, and maintain their triboelectric charging characteristics and A.sub.t for an extended number of imaging cycles, exceeding, for example, it is believed, 50,000 in a number of embodiments. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic imaging and printing processes, including color processes.
Toner, developer compositions, and processes thereof are known. For example, there are illustrated in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition comprised of resin and pigment. Further, there are disclosed in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions with resin particles and pigment particles, and as charge enhancing additives alkyl pyridinium compounds. Additionally, other patents disclosing positively charged toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014, 4,394,430, and 4,560,635, which illustrates a toner with a distearyl dimethyl ammonium methyl sulfate charge additive.
Moreover, toner compositions with negative charge enhancing additives, and processes thereof are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resin particles, pigment particles, and as a charge enhancing additive ortho-halo phenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives.
There is illustrated in U.S. Pat. No. 4,404,271 a complex system for developing electrostatic images with a toner which contains a metal complex represented by the formula in column 2, for example, and wherein ME can be chromium, cobalt or iron. Additionally, other patents disclosing various metal containing azo dyestuff structures wherein the metal is chromium or cobalt include U.S. Pat. No. 2,891,939; 2,871,233; 2,891,938; 2,933,489; 4,053,462 and 4,314,937. Also, in U.S. Pat. No. 4,433,040, the disclosure of which is totally incorporated herein by reference, there are illustrated toner compositions with chromium and cobalt complexes of azo dyes as negative charge enhancing additives. These and other charge additives can be selected for the present invention, with P51, quaternary ammonium salt, at 0.5 to 2.0 percent, available from Orient Chemicals being preferred.
In U.S. Pat. No. 5,082,761, there is illustrated a set of toners comprised of an initial supply toner and a supplementary toner, both of which are comprised of toner powder and additives on the surface.